In prior computer systems, a user is forced to a identify free interrupt request level (IRQ) before adding a new I/O device to the computer system. If the user is not aware of the IRQ used by each device in the computer system then identifying a free IRQ becomes time consuming. The user must try IRQs at random until a free IRQ is found.
One prior solution to the problem of identifying free IRQs includes a special application specific integrated circuit (ASIC) and a resistor for each IRQ line. In addition to the cost associated with the ASIC, this solution suffers from another disadvantage. This solution depends upon specific behavior by other I/O devices in the computer system. When I/O devices do not behave in the expected manner, the prior hardware solution cannot be depended upon to accurately identify free IRQs.